1. Field of the Invention
The present invention relates to an electronic still camera for photographing a still image using a memory.
2. Related Background Art
In order to obtain frame data of still images (obtain two, i.e., odd and even fields) using an electronic still camera, an image pickup element comprising color filters which repetitively appear at two-pixel periods in the vertical direction shown in FIG. 1A or 1B must be used. As shown in FIGS. 1A and 1B, since a conventional image pickup element alternately reads out odd- and even-numbered rows in odd and even fields, the two outputs must be the same.
However, when the image pickup element comprising the color filters shown in FIG. 1A or 1B is used, two row data obtained from every other row, for example, 1st- and 3rd-row signals for an odd field, and 2nd- and 4th-row signals for an even field must be used to extract luminance signals and color signals. For this reason, since a vertical distance between data becomes large, vertical correlation is reduced, and a generated amount of false colors is increased.
In signal processing, a large number of 1H delay lines are required to extract luminance and color signals.
When interlaced scanning is performed using an image pickup element (e.g., a CCD: charge-coupled device) having color filters aligned as shown in FIG. 2, in, e.g., a video movie camera which can perform a field-sequential read operation, vertically read access ((n)th and (m)th rows are mixed and read out in the first field, and (m)th and (n+1)th rows are mixed and read out in the second field) thereby alternately outputting a line having signals C.sub.1 =(Mg+Cy) and C.sub.2 =(Gr+Ye) and a line having signals C.sub.3 =(Mg+Ye) and C.sub.4 =(Gr+Cy) in respective fields.
Therefore, luminance (Y) signals can be obtained in respective lines as Y.sup.1 =C.sup.1 +C.sup.2 =(Mg+Gr+Cy+Ye) and Y.sup.2 =C.sup.3 +C.sup.4 =(Mg+Gr+Cy+Ye), and color signals are obtained as difference signals between adjacent pixels like C.sub.b =C.sub.1 -C.sub.2 and C.sub.r =C.sub.3 -C.sub.4. Therefore, color difference signals given by the following equations are output for each line. ##EQU1##
The Y and C signals are then subjected to signal processing such as band limitation, y-conversion, white balance adjustment, and the like, normally executed in each field although not shown, thus obtaining a frame image.
However, an image pickup device such as a still video camera exclusively used for a frame-sequential read operation cannot perform vertical two-pixel mixing read access in units of fields unlike in a movie camera. Therefore, if the color filters aligned as shown in FIG. 2 are used, only Mg and Gr data are obtained in the first field, and only Cy and Ye data are obtained in the second field. Thus, a frame image cannot be obtained by a conventional arrangement.